MN NWAC Risk Common Name Latin Name Assessment Worksheet (04-2011) Palmer Amaranth Amaranthus palmeri Reviewer Affiliation/Organization Date (mm/dd/yyyy) Roger Becker University of Minnesota 8/08/2014 Box Question Answer Outcome 1 Is the plant species or genotype non-native to Yes, non-native in Minnesota. Is native to the southern Yes. Go to box 3. Minnesota? U.S. and Mexico; native to North America. 2 Does the plant species pose significant human or livestock concerns or has the potential to significantly harm agricultural production? A. Does the plant have toxic qualities that pose a significant risk to livestock, wildlife, or people? B. Does the plant cause significant financial losses associated with decreased yields, reduced quality, or increased production costs? 3 Is the plant species, or a related species, Yes. Palmer amaranth is a severe problem in summer Yes. Go to Box 6. documented as being a problem elsewhere? climates similar to Minnesota. (see Hager 2013; Hartzler 2014a; and Legleiter and Johnson 2013). It has not been documented as a problem in states with winter climates similar to Minnesota, but it is anticipated it will do very well since it is an annual with a seedbank and seedlings that have performed well in states with freezing winter temperatures, and portions of the growing season in Minnesota are similar to locations further south where Palmer amaranth is a severe problem. 4 Is the plant species’ life history & Growth Yes, documented in disparate articles, but oddly no Blue text is provided as requirements understood? classic biology of Palmer amaranth review article additional information could be found. not directed through the decision tree process for this particular risk assessment. 5 Gather and evaluate further information: (Comments/Notes) Box Question Answer Outcome 6 Does the plant species have the capacity to establish and survive in Minnesota? A. Is the plant, or a close relative, currently Yes. Palmer amaranth is not established in MN but a Yes. Go to Box 7 established in Minnesota? close relative, tall waterhemp, is. Tall waterhemp (Amaranthus tuberculatus (Moq.) Sauer), is common in Minnesota, and is similar to Palmer amaranth in that tall waterhemp is competitive, diecious, and resistant to several mode of action herbicide groups. Competitiveness of Palmer amaranth here is not known. We anticipate it would be very competitive similar to, or exceeding that of tall waterhemp (Bensch et al. 2003). Note: Amaranthus rudis and A. tuberculatus are now considered a single species, A. tuberculatus, common name, waterhemp (Pratt and Clark 2001). B. Has the plant become established in areas Palmer amaranth occurs at problematic levels in Blue text is provided as having a climate and growing conditions southern Indiana, Illinois, Missouri, and Nebraska. It additional information similar to those found in Minnesota? has recently been found in South Dakota, in five not directed through the locations in Iowa (Hartzler 2014b), and in one location decision tree process for in Wisconsin (Davis and Recker 2014). this particular risk assessment. 7 Does the plant species have the potential to reproduce and spread in Minnesota? A. Does the plant reproduce by No. No. Go to Box 7c. asexual/vegetative means? B. Are the asexual propagules effectively dispersed to new areas? C. Does the plant produce large amounts of Yes. Sexual, diecious reproductive system. Produces up Yes. Go to Box 7f. viable, cold-hardy seeds? to 460,000 seeds per plant with competition, 1 million seeds per plant when grown without competition (Sosnoskie et al. 2014). D. If this species produces low numbers of viable seeds, does it have a high level of seed/seedling vigor or do the seeds remain viable for an extended period? E. Is this species self-fertile? Box Question Answer Outcome F. Are sexual propagules – viable seeds – Yes. Palmer amaranth seed are readily dispersed locally Yes. Go to Box 7i. effectively dispersed to new areas? and over long distances, moved with farm equipment, feed stocks, and livestock. It is rapidly dispersed across agricultural landscapes where it has become problematic. Dispersal has been documented in cotton meal used in livestock feed rations (Davis and Recker 2014). G. Can the species hybridize with native Palmer amaranth has been shown to hybridize with Blue text is provided as species (or other introduced species) and tall water hemp (Franssen et al. 2001). additional information produce viable seed and fertile offspring in not directed through the the absence of human intervention? decision tree process for this particular risk assessment. H. If the species is a woody (trees, shrubs, and woody vines) is the juvenile period less than or equal to 5 years for tree species or 3 years for shrubs and vines? I. Do natural controls exist, species native to No. No. Go to Box 8. Minnesota, that are documented to effectively prevent the spread of the plant in question? 8 Does the plant species pose significant human or livestock concerns or has the potential to significantly harm agricultural production, native ecosystems, or managed landscapes? Box Question Answer Outcome A. Does the plant have toxic qualities, or No, with one notable exception. Nitrate poisoning in No. Go to Box 8b. other detrimental qualities, that pose a livestock from consumption Amaranthus species or significant risk to livestock, wildlife, or common lambsquarters has occurred when both of the people? following occur: a.) conditions exist that promote excessive N accumulation and b.) pigweeds comprise a significant portion of the forage available. For example, this has occurred in field corn where high levels of nitrogen fertilizer have been applied but the crop subsequently fails such as following hail, out or in a drought where silage is harvested rather than taking the crop to yield grain. High percentages of the forage harvested are often pigweeds due to excessive growth due to low crop competition coupled with high nitrogen nutrient levels. B. Does, or could, the plant cause significant Yes. Up to 91 % yield loss in corn (Massinga and Yes. Go to Box 9. financial losses associated with decreased Currie 2002; Massinga et al, 2001), and 79 % in yields, reduced crop quality, or increased soybean (Bensch et al. 2003). Palmer amaranth is one production costs? of the most aggressive weeds in cropping systems in the south, southeast, and lower Midwest. It is threatening the ability to use conservation tillage (Price et al. 2001), is very competitive, is tolerant of shading (Jha et al. 2008), and has been shown to be allelopathic (Menges 1987 and 1988). Is not a host of arbuscular mycorrhizae fungi (Moyer-Henry et al. 2003). C. Can the plant aggressively displace native species through competition (including allelopathic effects)? D. Can the plant hybridize with native species resulting in a modified gene pool and potentially negative impacts on native populations? E. Does the plant have the potential to change native ecosystems (adds a vegetative layer, affects ground or surface water levels, etc.)? Box Question Answer Outcome F. Does the plant have the potential to introduce or harbor another pest or serve as an alternate host? 9 Does the plant species have clearly defined benefits that outweigh associated negative impacts? A. Is the plant currently being used or No. No. Go to box 10. produced and/or sold in Minnesota or native to Minnesota? B. Is the plant an introduced species and can its spread be effectively and easily prevented or controlled, or its negative impacts minimized through carefully designed and executed management practices? C. Is the plant native to Minnesota? D. Is a non-invasive, alternative plant material commercially available that could serve the same purpose as the plant of concern? E. Does the plant benefit Minnesota to a greater extent than the negative impacts identified at Box #8? 10 Should the plant species be enforced as a noxious weed to prevent introduction &/or dispersal; designate as prohibited or restricted? A. Is the plant currently established in No. No. List as a Minnesota? prohibited/eradicate noxious weed. Box Question Answer Outcome B. Does the plant pose a serious human No. No. Go to 10c. health threat? Blue text is provided as additional information not directed through the decision tree process for this particular risk assessment. C. Can the plant be reliably eradicated If Yes – List as a prohibited/eradicate noxious weed. Yes – List as a (entire plant) or controlled (top growth only Yes when first discovered in MN, if scout and take prohibited/eradicate to prevent pollen dispersal and seed action on satellite populations since is not established noxious weed. production as appropriate) on a statewide in MN (yet - to our knowledge) eradication would be basis using existing practices and available possible and reasonable. If becomes more widely No - list as a restricted resources? dispersed before eradication steps taken, eradication noxious weed. would no longer be feasible, classify as a prohibited noxious weed. In these scenarios, the answer to 10a Blue text is provided as would be YES, 10b would be no, and 10c would be additional information YES. Then this risk assessment would direct to list as a not directed through the prohibited/eradicate noxious weed. decision tree process for this particular risk If No - list as a restricted noxious weed. Once present assessment.. in MN and a few new infestations are allowed to escape, it may be difficult to control if introduced populations are resistant to multiple modes of action of herbicides used in major commodity crops. In that case it would spread rapidly through excessive seed production. If that occurs, the answer to 10a would be YES, 10b would be no, and 10c would be NO. Then this risk assessment would direct to list as a restricted noxious weed – but that is not an acceptable designation for an agricultural row-crop weed where dispersal could not be prevented.